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Month: December 2011

A new optical clock that is twice as accurate as any other has been unveiled by physicists in the US. The clock, which is based on a single aluminium ion, could remain accurate to within one second over3.7 billion years. The previous record was held by a clock with one mercury ion, which was good to one second in 1.7 billion years.This clock use a different principle quantum-interference protocol which makes it more accurate. Very soon this will be replacing our atomic clocks.

Stability is a must

An optical clock has three main components. The first is a highly stable “reference” frequency provided by a narrow optical absorption line in an atom or ion. The second element is a feedback system that “locks” the output of a laser (called the local oscillator) to the reference frequency. The third component provides a very precise
measurement of the frequency of the laser – usually with a “femtosecond comb”.

The most important component, however, is the atom or ion itself – which must absorb light over an extremely narrow and extremely stable frequency range. To ensure this, the atom or ion is isolated in a vacuum chamber and cooled to near Continue reading →